stuffing
 

can anybody tell me if the reedvalve engines such as ryobi respond too stuffing the crankcase.

stuffing
 

A lot of people try to get the back plate as close to the crank as they can. ( @ .010" clearance ) but I havn't read about anyone putting cork above the wrist pin under the piston?

Enjoy,

Jim

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Thanks yes I was refering to decreasing the back plate clearance I hadn't heard of cork above the wristpin eather but it is a thought.

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Can someone explain how reduction of that space would improve performance (hp)?

understand how reducing head / case gasket could increase compression, but not the former.

stuffing
 

the crankcase in a two stroke is used as an air pump so if you increase its compression ratio you make it more effecient.

i've read about the cork trick in a model engine book from the fifties and even back then it wasn't recomended because it would cause the piston crown to overheat.

dave

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Dave : got it. thanks Mike

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Don't waste your time with stuffing. I used to do it when I worked for Kawasaki tuning the Greenstreak 100's. Power gain was negligible if at all. There are many other better methods for performance improvement.

Max

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Max,
I beg to differ. In some engines an appreciable amount of increase is achieved through stuffing. We have tested several different mods and for the money stuffing is well worth the money (free). If you would like more details or pics please feel free to contact me directly at [email protected]

sincerely,
flyguy2002

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for the most part i agree but if you like tinkering there are always gains in power to be found. duke fox once ADDED the volume of the backplate to a .60 and gained power! i've also seen gains when unstuffing piped engines but nothing major.

dave

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The way I heard it on the Duke Fox crankcase volume story is that he machined out a back plate straight through and put a O-ringed piston in it that was screw adjustable. Then he measured engine rpm while adjusting the piston in and out. He found that the best running position was not all the way in.

There must have been a resonant position?

Enjoy,

Jim

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Not so much a resonant tuning. but more likely a pumping efficiency optimization. Every IC engine, whether it is the Otto cycle gasoline engine or the Diesel Cycle, well, diesel engine, is essentially an air pump, whose efficiency depends on many factor: CR, port timing, intake & exhaust plumbing, etc.

What Duke Fox found was probably a crankcase volume at which that particular combination of engine parameters resulted in the best pumping efficiency.

If you got gobs of time and patience on your hands and don't mind the possibility of gaining zilch in the end, then by all means experiment. Power gain is possible but by no means guaranteed.

stuffing
 

Browsing thru a Motorcycle magazine I saw a picture of one of the new super hot two stroke engines...The crank had nylon stuffers bolted to the insides of the crank webs...Must work on some engines....